In the prior art of lifting devices, a persistent problem has been that of locking of the elevated elements thereof in response to a system failure during ascent or descent of the system.
In the prior art, as is reflected in U.S. Pat. No. 3,117,765 (1964) to Chiuzzi entitled Lifting Device, the standard approach to so-called locking plate or safety interlocks is that of employment of sawtooth or serrated complementally interlocking teeth such that, as the members of the lifting system are elevated, such serrated teeth will slide over each other, and will rest slightly above each other during normal descent.
A shortcoming with the structures of the prior art is that in those instances where the teeth must be interlocked, i.e., when one surface must touch the tip or outermost surface of an opposite serrated surface, damage to the sharp ends of the sawtooth or serrated edge surfaces will often occur. Such damage to the mechanism may interfere with the overall operation of the lift system and, as well, may give rise to a safety hazard in and of itself.
Problems of the above type have become particularly prevalent in automotive lift systems known as parallelogram systems, which are typically above-ground automotive hydraulic lifts. When damage occurs to the interlocking safety plates of such a system, the stability of, for example, a fifty ton truck resting upon a structure may be impaired. Also the truck may be left stuck in the air.
It is as a response to the above set forth needs of the prior art that the instant invention may be viewed.